Ion implantation is a process of introducing dopants or impurities into a substrate via bombardment. In semiconductor manufacturing, the dopants are introduced to alter electrical, optical, or mechanical properties.
Ion implantation systems may comprise an ion source and a series of beam-line components. The ion source may comprise a chamber where ions are generated. The ion source may also comprise a power source and an extraction electrode assembly disposed near the chamber. The beam-line components, may include, for example, a mass analyzer, a first acceleration or deceleration stage, a collimator, and a second acceleration or deceleration stage. Much like a series of optical lenses for manipulating a light beam, the beam-line components can filter, focus, and manipulate ions or ion beam having particular species, shape, energy, and/or other qualities. The ion beam passes through the beam-line components and may be directed toward a substrate mounted on a platen or clamp. The substrate may be moved in one or more dimensions (e.g., translate, rotate, and tilt) by an apparatus, sometimes referred to as a roplat.
In many ion implanters a downstream electrostatic module, may function as an electrostatic lens to control ion beam energy, ion beam shape, and ion beam size. The electrostatic module may accelerate or decelerate an ion beam to a final energy, while altering the direction of the ion beam. By altering the direction of the ion beam, energetic neutrals may be screened out, resulting in a final beam having a well-defined energy.
Known electrostatic modules may employ, for example, multiple pairs of electrodes, such as seven upper and lower electrodes arranged in pairs, where the electrodes bound and guide an ion beam traveling therethrough. The electrodes may be arranged as rods spaced equidistant from an ion beam. The rod/electrode potentials are set to create electric fields in the electrostatic module causing the ion beam to decelerate, deflect and focus the ion beam.
The electrostatic module often is configured with suppression electrodes designed to accelerate the ion beam to a maximum negative potential in the case of positive ion beams, generating a suppression of electrons at the same time. Notably, changes in the suppression voltage applied to suppression electrodes may cause beam focusing to vary in a complex manner. Under various sets of conditions, the beam height may be controlled by varying the suppression voltage. As suppression voltage increases, beam height decreases, providing a control “knob” to adjust beam height delivered to a substrate. When overall beam energy is to be low, suppression voltage applied to the suppression electrodes may also be low.
With respect to these and other considerations, the present disclosure is provided.